This is a workflow which lets you look up how much you have left in a You Need a Budget (http://www.youneedabudget.com) category for the current month.
It looks for your budget file in ~/Dropbox/YNAB and ~/Documents/YNAB. If you have a single budget in one of those folders, it will use that and needs no configuration. If you have multiple budgets, or a budget somewhere else, you can use a File Action on it to select it as the budget to use.
Fuzzy/substring matching, tries to use the currency symbol/format based on the budget's configuration.
Hacked up the code to parse the YNAB data myself, so please make sure that it's reporting accurately for you and let me know if not!
Download here: http://cloud.jamesoff.net/0J2t2614191h (Updated 2014-10-21)
(System Python, no extra dependencies or libraries required.)